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I need to run cable to my 12v recovery winch. Run is 15 ft from battery. Winch info says at full load it pulls 400 amps. Instead of running one positive lead due to the size it would need to be i need advice on size of two copper cables to run side by side. I would have the lugs crimped and soldered . I would like to use class m 34 awg welding cable due to flexibility. What size cable do i need for this double run and how best to run the ground and size of ground on vehicle. I was wanting to use either two runs fo positive and two for negative of 1/0 or 2/0 instead of one run each of 4/0 since 4/0 is 7/8” diameter.

Richard Powell
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  • The place that you get the lugs crimped on would probably know. I found some 4/0 gauge cable with a current capacity of 405 A. In view of the high current, it would be safer to have it installed by someone who has professional indemnity insurance. IMHO. – Andrew Morton Jan 21 '18 at 16:22
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    Based on the ampacity tables I am finding online, you would need to use 3/0 AWG minimum. Each run of 3/0 can support 240 A. If you are relying on the chassis as the negative return conductor, you need to make sure the electrical connection from winch to chassis is up to the job or you will not get full power at the winch. It would be best if the cable is not energized except when you are actually operating the winch. A short circuit while driving could cause any number of problems. – user57037 Jan 21 '18 at 16:30
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    Don't run 400A return through the chassis! That will for sure be unreliable. You will want to make the wires the same cross section (both wires carry the same current) and the cable run as short as possible, of course - but also well protected from physical wear. You don't want the + wire shorting to the chassis with practically no fuse at all. Something will overheat. Be wary of sharp points where the wires can rub through the insulation. – MrGerber Jan 22 '18 at 04:58

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I don't have the current capacity for the cable you quote, but I fitted an electric winch to an HGV tractor and trailer a long time ago. If your cable is under or close to 400A then running two in parallel will work as well. If you have not bought the cable yet - then go up to 600A...

I used flexible 600A welding cable (this is only 1/2" or 5/8" diameter from memory) and soldered the lugs both ends. The idea was that the cable was stored clamped / fixed to the tractor unit 24v battery cover, then once the trailer was in position the cable could be connected to the winch - used quick-release connectors for that.

The reason was that the original fitting of this winch was only done with one cable - the live - to the winch and it then relied on the trailer earthing via the 5th wheel - this did not work reliably and it partially burnt out the wiring on the truck... I had to repair all that damage as well...

Owner was very happy as it worked fine and never destroyed the indicator unit again (apparently he had purchased 5 in the past due to the winch earth...)

Solar Mike
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